Summer doesn’t remember her past but when she does….probably all of it.

Nettle ultimately would decide to not go to the town the day yveltal attacked it, although she debates saving her starter. Shes healed since then.
Weiss is honestly fine with how her lifes gone. It wasnt the prettiest, but its hers. Orchid's the same.
Astra wouldve never gone up that mountain to train, where she got attacked by a beartic and gained a fear of ice pokemon

Alexis would want to prevent themselves and Zestasia from encountering a Houndoom when they were younger that led to Zestasia going missing, and Alexis injuring their arm.
Kayla would simply like to not be sent into the far flung future and stay in her own time with the people she loved

HOO BOY would many of my cast have a field day with that question. From Jolty finding a way to save her sister's life to Kaito hoping for his family to not have perished, or Icebella finding a way to have no destroyed her friendships...or Sabi wishing to have not lost her eye.

On the flipside, many of them found good things THROUGH those tragedies so they'd also argue that changing the present they have now wouldn't be as ideal as one would think.

Ruth: would not change anything about her past because she doesn't know... much about what happened.

Kingston: I suppose he'd make it so that his parents hadn't split up and he hadn't gone back to the Crossbell family. He just wanted a normal life and that got upended when his grandfather used his parents divorce to pressure his mom to return home.

Easily, Elio would prevent his parents, maternal grandmother, and his adoptive mother - "Adiunna, the Volcarona" from dying at the hands of Pokemon Hunters/Poachers.

Stephanie would stop trying to find Arthur’s cure, just so she could spend more time with her dying husband.

Ilex would go back to when she was a kid and put less focus on school and make some freaking friends.

Labi: “oh… I was just going to get extra time to think of a catchphrase and fandom name…”

There's a whole laundry list of things Odd wishes could end up differently, but he came to understand that many of the things he wanted to change were far out of anyone's control, even with direct intervention.

But if he had to choose ANYTHING, he'd probably just want to spend more time with his father

Lex would never have taken his younger sister into the mines near their home. She had wanted to try to catch a Pokemon, but Lex didn't want her to go unsupervised so he went with her.

The accident that happened that day left his younger sister paralyzed.

For Norra, would have wished to have actually sought after where her parents disappeared to. Try to find some leads, at least vs letting her depression getting the better of her when she returned their house in Sinnoh.

The answers for both Jin and Mary would be same and they'd just want more time with their parents ;-;